Bore crown for percussion drilling



June 9, 1953 D. w. HAGLUND ET AL BORE CROWN FOR PERCUSSION DRILLING Filed Feb. 28. 1949 lA/VENTORSJ Patented June 9, 1?53 BORE 2 CROWN FOR PERCUSSION DRILLING 'Didrik"Will'1-elm-= Haglund, Sanflwiken; and Sven Erik Elstrfim, Stockholm, Sweden, assignors to Sandvikensv J'emvcrks Aktieholag; .Samdvi'ken, Sweden, a. jnintqstock companm'ofiaswcclem Application "Fe'brnary'ZS, 1949;?Seria1. No. "18332 .Im1.S-weden Februam 28, .1948

-9 Glai'mss (Cl. 255-64 Tihis'inventlon' relates to a bore:- crown for gercussiondrilling; provided with two separate cutting; elements, of" hard" metal; 1;, .e, alloysof hard; carbides, nitrides silicides; bori'dcs etc; which have. been sint'ered together {by :means' of one. or more metals from the, iron. group.

Percussion borers with'hard metal cuttin elements as hitherto usually usedare providedgwith: a: simple chiseledge. which is securedto the bore crownrandihasthe shape of a plane; disc or the" like. having; aucuttingg edge and standing edge Wise-fin. a..slfot of" the bore: crown. Very; good re: sults have been obtained with such, cutting-elementsin most rocks. In cracked" rocks andiin certain very hard andvwearing rocks the results willbeynoorer. Now; experience has shown that bore crowns'xwith more: cutting elements are tobe. preferredrin. said" rocks and? thatverygoodyields are. obtained with; these. multiple-edge crowns; However; in. these types: of. drills; at least toursurfaces have to be: ground. Compared with drills havinga simpl'echisel edge and thusmerely two grinding' surfaces: the re -grinding'oIithemultiple-edge dril1s:is essentiallymore ditficult and sinceit" isnot ossible with. advantage: to utilizethe same grinding'device-f'or, both:

types. of drills the: multipleredge dril1s"have--notcome intnamcre general-use; I 'Ihepresent invention relates to; a bore croswn fonnercussion driiling provided with twosepaa rate cutting: elements made of" hard metal'gand the main object Of"'llll8 invention is to providesuch a, borecrown; which merely'cneedi be ground;

along? two surfaces, vizz one surface ateachcutting'edge; or; more? exactly; theirouter sides-r- As' the grinding surfaces 'inthis casehave the same on approximately the! same angles of- :inlclination as the corresponding surfaces flof a andi are: scented in; recesses in. the; bore crowm inrsncha manner that a1 broad; side of the cut! tin elementlwill facethe centre axis-loft the borecrown andtlie entirely or partly open, exposed-or irea. Moreover, the broad sides; of: the cutting elements. facing the, centre: axis eithe: bore. crown preferably, form an acute. angle to planes extending, through; and including the centre axis a (lithe; bore; cr-o wnl Rreferablv, said: angles are chosen. between, 30? and 75?, especially, about,- 45". It should be noted, however, that the two Figures "5. and .6 shows a modification of the bore crown in side"- view and plan view-respectively:

Finally, Figureis a: cross sect-i'on of a of a bore-crown on' a. larger-scale;

Itshould" be noted that? similar parts in the several figures are indicated by' the same-refer ence-charact ers: inFigures '5 and-6 with-theaddition'of the let-ter=a.

the borecrown illustrated in Figures 1-'-4 two-cutting elements! and z of hard metal have a substantially plate-like shapeof rectangular or." paralle'l-t-rapezoid cross-section; The eie'-- ments are secured inslots or-recesses 3 and 4' a drillliead' 2'3; The-two recesses form seatsfor the-cutt-ingelement's andare pref erably' disposedl at an angle to' one another and they havea shape corresponding tothe cutting elements: thus'thetwo'irecesses:fbrmtogether a-recess" having opnosite diverging faces 5,- 6= forming; an oldtuse angle-at 5; 61 'In the embodiment shown in Figure- 5" the correspondingabutments of" the{ recesses 3a; 4a may be-rounded or=rorm-pockets-= at 1; 8j-bnt; of course, any other suitable shape may be chosen. Preferably, as, showni-in Figure- 7; thewidth B of" each cutting' element (1b; T5); is essentiallygreaterthan its height H5 The cutting element need not necessarily have paral lel or generally parallel sides; but also" cutting eiements shaped in some other manner may- "be used. Moreover; the cutting element's need not?- be undivided but' also'divided cutting" elementsa suitable angle a (Figure '7), preferably at an acute angle ranging from 30 to 70. The opposite sides of the cutting elements rest directly against the inclined recesses. The elements I. 2 are spaced apart by a free surface 2| at the centre portion of vthe bore crown.

During the grinding operation it is merely necessary to grind the outer sides 9, I which lie entirely open or exposed and farther away fromthe centre axis A and are narrower than the inner sides II, I2, which, as aforesaid, lie entirely orpartly open or exposed. In Figure '7 the planes axis of said drill head in at least partly exposed ca, b-b, cc, d--d indicate the new surfaces of the cutting element beyond the initial cutting surface 2e and the adjacent surface of the bore crown after regrinding. It is clearlyseen (that practically the entire cutting elements lb, 2? may be utilized by such successive regrindings according as the cutting elements are worn out. The

inner end surface or edge 2d abuts the inner end ofeach recess, while the greater fiat side 20 lies ineach'inclined recess.

l L-In order to get a convex shape of the cutting edges I3, I4, which usually is desired, the. outer surfaces}, II] are ground slightly curved (Figure 2). The edge angle or tool angle (that is the angle between the sides 9, II and I0, I2 respectively) may either be equal for all parts of the cutting lements I, 2 (Figures 1 and 2) or it may be greater at'the outer ends of the cutting edge I3a, I4a than at the centre portion thereof (Figure 6), the intermediate portions of the cutting edge passing through a smooth transition from one edge angle to the other. The purpose of having greater edge angles or tool angles at th outer ends than at the centre part of the cutting element is mainly to comply with the de'sideratum of obtaining great resistancy at the outer parts of the cutting element which during drilling are exposed to the greatest stresses.

The end surfaces I5, I6 of the cutting elements (Figures 2 and 4) at the periphery of the bore crown normally form an acute angle to the inner sides II, I2 of the cutting elements. According to the embodiment in Figure 4 the outer portions of these parts have been ground off so that the sides I I a, I2a pass into the end surfaces through a smooth rounding. In this manner it may be possible to diminish the danger of cracks developing in the cutting elements which could occur.

dueQto said acute angles.

Between the cutting elements I, 2 there may be cut grooves I'I, I8 in drill head 23a at the periphery of the bore crown in axial direction for the purpose ofdischarging boring. dust which is collected between the cutting elements. One or more, channels I9 (Figures 1-3) forsupplying. flushing medium to the said grooves or to the bore hole communicate with a centre channel 22- for'such medium. Figures 5-7 show a similar centre channel 20 which opens at the surface drilling including a drill head having a pair of.

inclined recesses diverging forwardly and disposed symmetrically with respect to the central axis at the working end of the drill head, each recess forming a seat for receiving and supporting a cutting element; and a pair of substantially fiat plate-like cutting elements of substanopen positions.

2. A rock drill or boring crown for percussion drilling including a drill head having a pair of inclined recesses diverging forwardly and disposed symmetrically with respect to the central axis at the working end of the drill head, each recess forming a seat for receiving and supporting a cutting element; and a pair of substantially 'flat plate-like cutting elements of substantially rectangular cross section, each having two relatively greater opposite sides of greater width than height and fournarrow sides or edges, the cutting elements being individually mounted on the drill head with one of the relatively greater sides of each cutting element fitting in one of the re-, cesses and the opposite relatively greater side of, the cutting elements facing said central axis of said drill head in at least partly exposed open positions, and the narrow side or edge of each, cutting element remote from the other cutting element and the central axis of the drill head being fully free and accessible for regrinding in such fashion that the regrinding of said narrow side or edge alone sufiices for resharpening of the ,1

cutting element involved.

posed symmetrically with respect ,to the central axis at the working end of the drill head, each recess forming a seat for receiving and support-' ing a cutting element; and a pair of substantially flat plate-like cutting elements of substantially rectangular cross section, each hav-.

ing two relatively greater opposite sides of greater width than height and four narrow, sides or edges, the cutting elements being individually mounted on the drill head with one-of the relatively greater sides of each cutting element flt.-.

ting in one of the recesses and the opposite relatively greater side of the cutting elements fac ing said central axis of said drill head in at least partly exposed open positions, and the narrow. side or edge of each cutting element remote from.

the other cutting element and the central. axis of the drill head being fully free and convexly.

boring crown for percussion drilling including a drill head having at its front end a recess formed with two opposite outwardly diverging faces, each of said faces constituting a support for a cutting element; and a pair of elongated fiat plate-like cutting ele-' ments each having two opposite elongated 'plate' faces and a plurality of elongated narrow edge faces connecting said plate faces, each of said cutting elements being individually mounted on said drill head with one of said elongated narrow edge faces located at an outwardly'located edge of said recess so as to be adapted to be ground, and with one of the plate faces thereof abutting against and supported by one of said opposite faces ofsaid recess, said cutting "'ele-" cutting edge upon eachv ments facing each other with the other plate faces.

5. A rock drill or boring crown for percussion drilling including a drill head having at its front end a recess formed with two opposite outwardly diverging faces, each of said faces constituting a support for a cutting element, each of said recess faces being formed with an abutment in the region of the apex of said recess projecting into said recess transversely to the associated face; and a pair of elongated fiat plate-like cutting elements each having two opposite elongated plate faces and a plurality of elongated narrow edge faces connecting said plate faces, each of said cutting elements being individually mounted on said drill head with one of said elongated narrow edge faces located at an outwardly located edge of said recess so as to be adapted to be ground, and with one of the plate faces thereof abutting against and supported by one of said opposite faces of said recess, said cutting elements facing each other with the other plate faces, at least one of said elongated edge faces of each cutting elements abutting against and supported by one of said abutments.

6. A rock drill or boring crown for percussion drilling including a drill head having at its front end a recess formed with two opposite outwardly diverging faces disposed at an acute angle to each other ranging from 30 to 75", each 7 of said faces constituting a support for a cutting element, each of said recess faces being formed with an abutment in the region of the apex of said recess projecting into said recess transversely to the associated face; and a pair of elongated flat plate-like cutting elements each having two opposite elongated plate faces and a plurality of elongated narrow edge faces connecting said plate faces, each of said cutting elements being individually mounted on said drill head with one of said elongated narrow edge faces located at an outwardly located edge of said recess so as to be adapted to be ground, and with one of the plate faces thereof abutting against and supported by one of said opposite faces of said recess, said cutting elements facing each other with the other plate faces, at least one of said elongated edge faces of each cutting elements abutting against and supported by one of said abutments.

7. A rock drill or boring crown for percussion drilling including a drill head having at its front end a recess formed with two opposite outwardly diverging faces, each of said faces constituting a support for a cutting element, each of said recess faces being formed with an abutment in the region of the apex of said recess projecting into said recess transversely to the associated face, said drill head having at least one lateral groove extending in axial direction of said drill head from the apex of said recess and adapted to receive drilling dust, said drill head also having an internal passage ending in said groove and head with one of said elongated narrow edge faces located at an outwardly located edge of said recess so as to be adapted to be ground, and with one of the plate faces thereof abutting against and supported by one of said opposite faces of said recess, said cutting elements facing each other with the other plate faces, at least one of said elongated edge faces of each cutting elements abutting against and supported by one of said abutments.

8. A rock drilling or boring crown for percussion drilling including a drill head having at its front end a recess formed with two opposite outwardly diverging faces, each of said faces constituting a support for a cutting element; and a pair of elongated fiat plate-like cutting elements each having two opposite elongated plate faces and a plurality of elongated narrow edge faces connecting, said plate faces, each of said cutting elements being individually mounted on said drill head with one of said elongated narrow edge faces being curved and located at an outwardly located edge of said recess so as to be adapted to be ground, and with one of the plate faces thereof abutting against and supported by one of said opposite faces of said recess, said cutting elements facing each other with the other plate faces.

9. A rock drilling or boring crown for percussion drilling including a drill head having at its front end a recess formed with two opposite outwardly diverging faces, each of said faces constituting a support for a cutting element; and a pair of elongated flat plate-like cutting elements each having two opposite elongated plate faces and a plurality of elongated narrow edge faces connecting said plate faces, each of said cutting elements being individually mounted on said drill head with one of said elongated narrow edge faces being curved and located at an outwardly located edge of said recess so as to be adapted to be ground, and with one of the plate faces thereof abutting against and supported by one of said opposite faces of said recess, said cutting elements facing each other with the other plate faces and having cutting edges formed by said other plate face and by said outwardly located narrow edge face of each' cutting element, the angle of the cutting edge of each cutting element being greater at the periphery of the drill head that at the central portion of the cutting edge.

DIDRIK WILHELM HAGLUND. SVEN ERIK ELsTRoM.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,191,493 Reilly Feb. 26, 1936 2,215,948 Williams Sept. 24, 1940 2,368,512 Zimmerman Jan. 30, 1945 FOREIGN PATENTS Number Country Date 73,268 Sweden Aug. 2, 1929 333,489 Great Britain Aug. 14, 1930 671,954 Germany Feb. 17, 1939 

